Interesting discussion, confirming what has seemed apparent over the years, viz. that appraisers really vary in their approach to the age issue. I appreciate the input here.
Honestly, and with no intent to impune anyone here, if there is section of the SCA grid which I've seen most utilized for value inflation (I'm talking the bad old days), it was related to effective age estimates and adjustments. It often seemed that appraisers came up with incredibly specific EAs for comps (thus appearing to be based on industry formulas), then made hefty adjustments favoring their subject-- which inevitably had a conveniently low EA despite the shag carpeting and harvest gold range. You've all seen it...
I've aways preferred condition adjustments, especially when my comps are of relatively competitive ages. You can base adjustments on the relation between estimated/actual costs of remodeling/updating and market return on value, the data of which seems more available and readily supported.
I share the philosophy referenced by others here regarding newer homes. I feel justified invoking age adjustments when houses built within the last decade or so are all in relatively the same C3 or C4 condition, but you feel there should be consideration for the difference between a 2 year-old and 10 year-old roof, or when the 10 year-old house is close to needing new exterior paint but is not yet specifically worn or defective, or the 10 year-old carpet is still in marketable condition, but obviously not as new as the 2 year-old, etc. This principle is typically supported by the difference between the prices of brand-new homes versus resales of those built a few years earlier.
Sometimes I will use an age adjustment when needing to use a comp of more dissimilar age for another of its characteristics, like needing to bracket my subject's site size or GLA, etc. If the comp is relatively similar in interior finish quality and condition, due to updating, but I feel there is a substantial difference in the collective construction techniques/materials of its core structure due to its year-built era, then I tend to think age is a better category for the adjustment. But I make it based on actual age, not so-called effective age.
I'm not discounting the value of seriously evaluating effective age based on methods referenced by folks in this thread, but I think the framers of the UAD and other recent industry changes recognized the inherent abuse in the use of EA as it was applied by rogue appraisers in the boom years...
